Recycling wood pulping chemicals by molten salt electrolysis: cyclic voltammetry of mixtures containing Na2CO3 and Na2SO4

We are investigating a novel electrochemical pathway for efficient recycling of inorganic chemicals from the kraft pulping process. To analyse this process, cyclic voltammetry was conducted on molten salts containing sodium carbonate, or sodium carbonate and sodium sulfate on gold and nickel/nickel oxide electrodes. Pure sodium carbonate at 860 °C was determined to exhibit oxidation to carbon dioxide and oxygen. Electrochemical reduction proceeded to both sodium metal and to sodium oxide and either carbon or carbon monoxide. A mixture with a 2.36:1 molar ratio of sodium carbonate to sodium sulfate at 860 °C was investigated where the anode again displayed carbonate oxidation. The cathode reactions are the reduction of sulfate ions to form sulfide and oxide ions and carbonate reduction to oxide ions and carbon monoxide. Separated cell operation to avoid oxide ion oxidation appears necessary according to the cyclic voltammetry. Nickel oxide was found to be a stable anode material in a sodium carbonate molten salt. This paper, based on cyclic voltammetry results of oxide ion production, is the first step towards a technical electrolysis process for recausticizing of molten smelt for the kraft pulping process.     

石灰拜耳法石灰添加方式探讨

本结合石灰拜耳法试验和当前常规拜耳法的生产情况，详细分析了添加固体石灰的危害性，提出利用循环母液化灰添加石灰乳的新工艺，对拜耳法生产节能降耗有一定的指导意义。     

Effects of different pretreatment processes on viscose fabrics in different types and properties

Abstract

In this study, the effects of different pretreatment processes on the properties of viscose fabrics (sulphur content, whiteness degree, weft yarn breaking force, crystallinity and fiber surface) and on the color efficiency and repeatability of the prints have been investigated. For this purpose, viscose fabrics obtained from different sources and containing different amounts of sulphur were causticized, bleached, and reductive-washed. After impregnation with urea, fabrics were printed with two reactive dyestuffs having the same reactivity, but different molecular sizes. Color values of both dyes were measured and fastness was tested and compared in order to observe the effects of different pretreatment processes. Different methods of sulphur analysis were also investigated and tested to determine the sulphur content of the fibres. Among these methods, the lead acetate method, which is a subjective evaluation system, has been selected as the most appropriate for practical working conditions of the plants, and a sulphur scale was formed according to this method. Accuracy of the scale was also confirmed by elemental analysis (CHNS–O) method.     

Thermodynamics and kinetics of the kraft causticizing reaction

A methodology for the calculation of the equilibrium of the causticizing reaction of pure sodium carbonate solutions at 100°C without any adjustable parameters is presented. The methodology is extended to compute the effect of sodium sulfide. The causticizing reaction was found to be slightly endothermic at 100°C. The caculated results were found to be in good agreement with experimental data. An empirical kinetic model for the causticizing reaction is also presented. The model takes into account the variations in both green liquor composition and lime quality and can yield the causticizing efficiency directly. The calculated results of the causticizing efficiency were found to be in good agreement with experimental data from several Canadian pulp mills and reflected the effect of the variation in lime quality.     

Ca（OH）2-Na2CO3反应体系工艺参数对白泥碳酸粒径控制研究

研究了Ca(OH)2-Na2CO3反应体系的碳酸钙粒径控制.研究结果显示:苛化工艺对苛化碳酸钙粒径具有不同程度的影响,对粒径影响程度按照高低顺序依次为消化热水温度、苛化温度、消化时间、搅拌速度和加料时间,其中消化热水温度和苛化温度是影响碳酸钙粒径的主要因素.随着消化水温度和苛化温度的增加,合成CaCO3颗粒粒度逐渐变小,但消化水温度超过60℃时,碳酸钙粒径基本保持不变.合成碳酸钙的陈化时间对其粒度有一定的影响,测试碳酸钙粒径时,陈化(静置)时间超过24h,测试结果较为准确.     

水合肼副产碱渣的回收工艺研究

研究了水合肼副产碱渣的回收利用途径,得到了工艺技术路线,考察了反应温度、时间、物料配比等工艺条件对Na2CO3苛化转化率的影响,当苛化反应温度为80～90℃,反应时间为100min,n（Ca（OH）2）：n（Na2CO3）为1．0～1．1时,产品质量合格,苛化转化率在90％以上。